YYEMPTY
#define yyclearin (yychar = YYEMPTY)
if (yychar == YYEMPTY && yylen == 1) \
yychar = YYEMPTY; /* Cause a token to be read. */
if (yychar == YYEMPTY)
yychar = YYEMPTY;
yychar = YYEMPTY;